Yesterday, the escalating communist revolution in the United States, graduated to full scale political assassination. This was left-wing terrorism. For Americans, this was a watershed moment and a wake-up call.

America seems to be crumbling, and more and more experts are comparing 2016 to 1968, which was defined by social unrest and violence.

In fact, many Americans in 2016 believe that things will get much worse before they get better.

Here are four reasons Americans are worried:

1. Social unrest. Micah Johnson shot 12 officers and killed five of them, and some in the country celebrated.

A hate group called the Black Power Political Organization sent out this chilling message after Johnson’s killing spree: “‪#‎BlackPower! ‪#‎BlackKnights! Sniper Assassins Take Down Five Police Officers! And More Will Be Assassinated In The Coming Days!”

Cops are being told to keep their law enforcement status secret when off-duty.

Officers have been told to carry riot gear and bulletproof vests with them on patrol.

Some officers fear fake 911 calls might be used to lure cops into an ambush.

Former Philadelphia police commissioner Charles Ramsey said on NBC’s Meet the Press June 10 that America is “sitting on a powder keg.”

Ramsey fears that there will be violence at the Democratic and Republican conventions. He’s not the only one; authorities in Cleveland are preparing to mobilize 5,000 police for the Republican National Convention, Off The Grid News reported. Local, state and federal authorities are preparing to spend $50 million on security preparations for the event.

2. Terrorism. Orlando gunman Omar Mateen, who pledged allegiance to ISIS, murdered 49 people in a gay nightclub – and ISIS is urging more attacks on America.

An ISIS propaganda video that surfaced on June 27 called for attacks on San Francisco and Las Vegas. The video praised Mateen and contained pictures of the Golden Gate Bridge and downtown San Francisco, CBS San Francisco reported. Former FBI agent Jeff Harp told CBS that he thinks the video is an attempt to incite more terrorist attacks.

3. The U.S. and worldwide economies. Despite the recent surge on Wall Street, most experts say the Brexit vote in the United Kingdom will wreak economic havoc, once the UK launches the mechanism to leave the European Union. CNN compared Brexit’s effect to how the 2008 financial meltdown impacted banks. One British bank, the Royal Bank of Scotland (RBS), lost 40 percent of its value. Shares of Germany’s Deutsche Bank (NYSE: DB) fell by 25 percent. Bloomberg writer Lisa Abramowicz and many traders think Deutsche Bank could soon collapse.

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“History may be repeating itself right here before our eyes, given the huge selloff in stocks after the Brexit results were known, and then the bounce back of stocks a few days later,” said Chuck Butler, the managing director of EverBank Global Markets.

4. Threats to the electric grid. Parts of southern California could face up to two weeks of blackouts this summer because a natural gas storage facility is unavailable, The Los Angeles Times reported. That includes Los Angeles.

A cyberattack also could knock out the electric grid. Hackers were able to knock out power to 225,000 people in the Ivano-Frankivsk region of the Ukraine on Dec. 23, 2015, using malware.

Many experts, including government officials, are worried the US will be the target of the next cyberattack. ISIS is trying to develop the capability for such attacks.

“We’ve seen the ISIS propaganda machine recruiting the brightest new computer minds and brilliant techs,” Miller Newton, the CEO of encryption company Pkware, told Fortune. “They’re building the capabilities to do cyberwarfare and it’s coming in a substantial way.”

Image source: NASA

In fact, the FBI and the Department of Homeland Security have begun issuing warnings to America’s power grid operators and other utilities about the serious threat of cyberattacks, Off The Grid News reported in April.

Other dangers to the grid include a solar storm that would take out the grid or an EMP attack from a country such as Iran or North Korea.

“North Korea wants to launch a satellite, and one of the greatest risks of the satellite is they would place a nuclear device in the satellite,” US Senator Ted Cruz (R-Texas) said earlier this year. “It would orbit around the Earth, and as it got over the United States they would detonate that nuclear weapon and set of what’s called an EMP, or electromagnetic pulse, which could take down the entire electrical grid on the Eastern seaboard, potentially killing millions.”

The Iranian military has studied the possibility of launching an EMP attack on the US electric grid, US Representative Trent Franks (R-Arizona) said. Franks said an Iranian document called “Passive Defense” describes such an attack, NewsMax reported.

“It outlined that the best way to deal with countries like America, a country that was much stronger than them, was an asymmetric strategy of attacking our electric grid,” Franks said of Passive Defense.

US Representative Lou Barletta (R-Pennsylvania) has warned that the grid would be down for weeks following an attack.

“If the goal of terrorists is to collapse our economy, then shutting down our electrical grid is where they would start,” Barletta wrote in a Roll Call op-ed. “Most troubling is the possibility that a cyberattack would be accompanied by a physical terrorist attack, a scenario that promises true havoc, panic and loss of life. The great challenge is that the threat continues to evolve, which only means that we are forced to evolve with it and be prepared for it.”

What do you think is the greatest threat to America? Share your thoughts in the section below: